Blood oxygenator utilizing a removable membrane oxygenator unit

ABSTRACT

An oxygenator for blood which comprises means for removably holding a membrane oxygenator unit, means for conveying blood to a patient through the oxygenator unit in a first flow path and back to the patient, and means for supplying oxygen gas through the oxygenator unit in a second flow path separated from the first flow path in the unit by a semi-permeable membrane. The oxygenator unit holding means carries a plate which has an oxygen inlet manifold port positioned to communicate with a mounted oxygenator unit, to provide a sealed oxygen flow path through the plate into the oxygenator unit.

United States Patent Leonard Dec. 30, 1975 [75] Inventor: Ronald .1. Leonard, Elk Grove Village, 111.

[73] Assignee: Baxter Laboratories, Inc., Deerfield,

Ill.

[22] Filed: Jan. 21, 1974 [21] Appl. No.: 435,143

[52] US. Cl 23/258.5; 128/DIG. 3 [51] Int. Cl. A6lM 1/03 [58] Field of Search 23/258.5; 128/DIG. 3

[56] References Cited UNITED STATES PATENTS 3,070,092 12/1962 Wild et a1. 23/258.5 3,396,849 8/1968 Lande et 21]... 23/2585 X 3,413,095 11/1968 Bramson... 23/258 5 3,480,401 11/1969 Holm et al.... 23/258 5 3,484,211 12/1969 Mon et a1. 23/258.5

3,506,406 4/1970 Birch 23/258 5 3,541,595 11/1970 Edwards 23/258.5 X 3,547,271 12/1970 Edwards 23/258.5 X 3,612,281 10/1971 Leonard 23/258.5 X

FOREIGN PATENTS OR APPLICATIONS 1,568,130 5/1969 France ..23/258.5 1,597,874 8/1970 France ..23/258.5

OTHER PUBLICATIONS A Pulsable Extracorporeal Membrane System; San Diego Symposium for Biomed. Eng-1963, (by Crescenzi et al.), pp. 27-31.

Primary Examiner-Barry S. Richman Attorney, Agent, or Firm-Louis Altman [57] ABSTRACT An oxygenator for'blood which comprises means for removably holding a membrane oxygenator unit, means for conveying blood to a patient through the oxygenator unit in a first flow path and back to the pa tient, and means for supplying oxygen gas through the oxygenator unit in a second flow path separated from the first flow path in the unit by a semi-permeable membrane. The oxygenator unit holding means carries a plate which has an oxygen inlet manifold port positioned to communicate with a mounted oxygenator unit, to provide a" sealed oxygen flow path through the plate into the oxygenator unit.

10 Claims, 5 Drawing Figures 4 i m 27 i lZb 29 1; 82 1 I as US. Patent Dec. 30, 1975 Sheet 1 Of3 3,929,414

PATIE NT US. Patent 1360.30, 1975 Sheath 3,929,414

37% in 2 mlhl- US. Patent Dec. 30, 1975 Sheet30f3 3,929,414

, BLOOD oxYGENATOR UTILIZING A REMOVABLEMEMBRANE OXYGENATOR UNIT BACKGROUND OF, THE INVENTION Membrane oxygenators for blood are attracting growing medical interest because of their capability of partially or completely taking over the respiratory function of a patient for a period of many hours and even days without unacceptable damage to the blood supply. Previously, bubble-type oxygenators involving the direct application of oxygen bubbles througha stream of blood had been used in open heart surgery for periodsup to four or five hours. However, unacceptable damage frequently is inflicted upon the blood supply of the patient if the bubble oxygenators remain in operation for periods significantly longer than this.

Commercially available disposable membrane oxygenator unitsare disclosed in US. pat. No. 3,757,955. The same patent describes a membrane oxygenator unit currently under development vin which the membrane is made of a porous, hydrophobic material such as 3 or 4 mil polytetrafluoroethylene sheeting having an effective pore diameter of .about 0.5 micron. Such materials are capable of rapidly transferringoxygen, carbon dioxide and water vapor, while preventing the transfer of blood itself through the membrane. Porous membrane oxygenator units exhibit an oxygen and carbon dioxide transfer capability which greatly exceeds the older membrane oxygenator unit designs which utilize thin silicone rubber membrane and the like. Accordingly, porous membrane oxygenator units can support the total respiratory needs of a patient with a significantly smaller total surface area of membrane than a conventional silicone rubber membrane oxygenator unit of similar design. As a result of this, the amount of blood which is removed from the body at any one time can be typically less with porous membrane oxygenator units, which is a significant and important advantage.

There is, however, a drawback to porous membrane oxygenator units: it is absolutely necessary for the pressure on the blood side of the membrane to at all times equal or exceed the pressure on the gas side of the membrane. If these conditions fail, the increased gas pressure may drive gas bubbles through the membrane into the blood flow path, from where the gas bubbles may be conveyed back to the patient. This could create a life-threatening embolism in the patient.

Accordingly, in US. Pat. application Ser. No. 390,567 filed Aug. 22, 1973 by Ronald J. Leonard, an oxygenator apparatus is provided for the safe and effective utilization of hydrophobic, porous membrane blood oxygenator units. In the device described in the patent application, a manometer means is provided to assure safe and reliable limitation of thegas pressure in the oxygenator unit.

Also, the aforesaid application discloses heat exchanging means and thelike for maintaining the appropriate blood temperature and other desirable parameters of operation.

For the commercial manfacturer of porous membrane blood oxygenator units, it is a matter of great importance to be certain that the customers utilize the oxygenator unit in a correct manner, using the correct equipment for mounting and supplying blood and oxygen to the membrane oxygenator unit, so that there will bles into the blood path, which can instantly createa life-threatening situation.

- ln'accordance with this invention, an oxygenator and membrane oxygenator unit for use therein are provided in which the membraneoxygenator unit is used only with great difficulty apart from the oxygenator itself, which can be designed to provide the necessary parameters of operation that result in safe use. Accordingly, a relatively foolproof system is provided for the protection of patients.

. Furthermore, in accordance with this invention, a system is provided for assured, unrestricted exhaust of gas, to prevent any'obstruction of the flow of gas from the oxygenator, unit, thus avoiding a consequent, potentially disastrous rise in thegas pressure of the'oxygen flow path in the oxygenator unit.

DESCRIPTION OF THE INVENTION The blood oxygenator of this invention comprises means for removably holding a membrane oxygenator unit, and means for conveying blood from a patient through the oxygenator unit, inv a first flow path and back to the patient The oxygenator also has means for supplying oxygen gas through the oxygenator unit-in a second flow path separate from the first flow path and separated from. it. in the oxygenator unit by a semipermeable membrane. In accordance with this invention, the means for holding the oxygenator unit is adapted to carry a plate in a position to engage the oxygenator unit installed in the holding means of the oxygenator. The platedefines an oxygen inlet manifold. port positioned to" communicate, while engaged with theoxy gena tor unit, with the inlet of the second flow path of the oxygenator unit, to provide a sealed oxygen flow paththrough thevplate into the oxygenator unit.

Asa result of this arrangement, oxygen comes to the plate by means of an oxygen .line, and is manifolded or spread into a wide flow path for delivery to the individ ual oxygenator unit flow channels by means of parts carried by the oxygenator itself rather than the oxygenator unit. As a result of this, oxygenator units desired for use with the device of this invention do not carry an oxygen manifolding means, and thus are not conveniently used with makeshift equipment. Hence, the user of a disposable oxygenator unit is strongly encouraged to utilize the standard equipment forthat unit with its tested safety features, rather than to incoiiv'eniently improvise his own arrangement of apparatus.

A typical membrane oxygenator unit defines blood and oxygen flow paths comprising a plurality of interleaving, parallel channels. It is contemplated thatthe opening around the inlets of the parallel channels, to provide the sealed oxygen flow path. The wide mouth opening of the oxygen inle t to the membrane oxygenator unit prevents the simple attachment of an oxygen line to the oxygenator unit, and thus encourages the use of the standard oxygenator equipment especially manufactured for use with the membrane oxygenator unit, which will include the necessary safety features such as a means for limiting gas pressure, a heat exchange unit, and the like.

Furthermore, in position of use the plate, with the exception of the manifold port area, is spaced from the membrane oxygenator unit in a position to overlie the gas outlet port of the second flow path of the oxygenator unit. Accordingly, oxygen gas escapes through the outlet port, then passing in many directions of flow between the oxygenator unit and the plate to the exterior. The advantage of this is that such arrangement greatly reduces the possibility of some accidental obstruction of the gas outlet port, such as might take place if the outlet port were a simple tube or opening. The reason this is necessary is that the accidental placement of some obstructing object, even momentarily, in front of the gas outlet port during operation could cause a sudden rise of gas pressure within the membrane oxygenator unit, which is dangerous for reasons discussed above.

IN THE DRAWINGS FIG. 1 is a schematic view of an oxygenator of this invention, with a porous membrane oxygenator unit installed in the holding means.

FIG. 2 is a rear plan view of the oxygenator unit holding means of this invention, with one side wall of the holding means removed, without an oxygenator present, and with the heat exchanger means shown in phantom.

FIG. 3 is a perspective view of the oxygenator unit holding means of this invention with a side wall removed, showing a typical membrane oxygenator unit prior to installation in the oxygenator unit holding means.

FIG. 4 is a side elevational view of the oxygenator unit holding means of the invention with the oxygenator unit installed, portions of the oxygenator unit and holding means being broken away and shown in section.

FIG. 5 is an enlarged view in vertical section of the vicinity of the oxygen inlet of the oxygenator unit as shown in FIG. 4.

Referring to the drawings, an oxygenator is shown which comprises, means 12 for removably holding a membrane oxygenator unit 14. Means for conveying blood from a patient through the oxygenator in a first flow path and back to the patient are also provided. Blood in inlet tube 16 is propelled through the oxygenator by a conventional roller pump 20, being drawn out of the venous reservoir 22. Blood is supplied to the venous reservoir through conduit 24 from the patients venous supply.

Downstream from the oxygenator, blood passes from the oxygenator into blood outlet tubing 18, and from there through heat exchanger 26 (such as disclosed in U.S. Pat. No. 3,640,340), to arterial reservoir 28 by tube 19, from where it is propelled by a second roller pump 30 into the patients arterial blood supply through conduit 32. Heat exchanger 26 is mounted on bracket 27 with its heat exchange fluid flow path inlet and outlet in communication with ports 29, which pass through bracket 27 of holder 12 for connection with a heat exchange fluid source.

A cardiotomy reservoir 34 can be provided to receive blood from a cardiotomy sucker which sucks blood from the patients incision site or the like, and passes it to the reservoir through line 36. The cardiotomy reservoir is connected by line 38 to a filter 40, which in turn connects with the venous reservoir 22.

Unit holding means 12 is held by bracket 35, which in turn carries a mast 37 having hangers 39, 41 for removably holding blood containing components of the oxygenator. Bracket 35 is in turn held on a hanger 43 which is attached to supporting member 45.

Referring also to FIGS. 2 through 5, details of oxygenator unit holder 12 and related parts are shown.

Holder 12 is shown to carry an oxygenator unit engaging plate 42, which in turn defines an oxygen inlet manifold port 44 which terminates at its inner end with an O-ring seal 46. A source of oxygen gas is provided through oxygen inlet line 48 to communicate with oxygen inlet manifold port 44, which provides a sealed oxygen flow path through the plate into the oxygenator unit.

Recessed portion 50 within O-ring seal 46 is provided to permit the oxygen gas to freely flow throughout the entire interior of O-ring seal 46.

Inlet manifold port 44, O-ring seal 46, and recessed portion 50 are positioned to communicate in sealing relation with the oxygen inlet 52 of oxygenator unit 14 as shown in FIGS. 3 and 5. As can be seen from FIG. 3, oxygen inlet 52 is elongated so that the many inlet ends of parallel flow channels 54 of conventional oxygenators are all directly exposed to the exterior of the oxygenator unit through inlet 52. O-ring seal 46, as part of the manifold port of plate 42, is proportioned to surround and seal inlet 52 of oxygenator unit 14 to provide a sealed oxygen flow path when unit 14 is installed in holder 12.

Oxygen flow path outlet port 56 of unit 14 is also typically elongated to permit the free exit of surplus oxygen gas, plus carbon dioxide and water vapor which is passed into the second flow path of oxygenator unit 14.

In FIG. 5, a typical construction of the layers which define flow paths 54 is shown. Porous, semi-permeable membrane 14M overlies support screening 148 in a convoluted, multilayer arrangement as further illustrated in U.S. Pat. No. 3,757,955. The edges of the membrane and screening are sealed together by a line of cured potting compound 14], and the structure is encased between walls 15, which are held together by fasteners 17 (FIG. 3).

As shown in FIG. 4, oxygenator unit engaging plate 42 is positioned to be spaced from and define an unbroken wall 58 over gas outlet port 56 of the oxygenator unit in position of use and separated by space 59, which is typically about US inch wide. As a result of this, exhaust gas from outlet 56 has unrestricted exit in a plurality of directions through space 59 between plate 42 and unit 14. The result of this is to greatly reduce the probability of accidental obstruction of outlet 56, since gas will vent adequately from oxygenator unit 14 as long as any substantial portion of elongated space 59 remains open to the exterior.

Plate 42 is attached to holder 12 by a removable nut 60 at one end and conventional detent means 62 at its other end, so that plate 42 is easily removable from holder 12.

Line 64 and conduit 65 through cover provide communication between the oxygen inlet manifold port 44 and safety means 66, held by bracket 27, for preventing the pressure of oxygen gas in the inlet manifold port from reaching a level sufficient to cause gas bubbles to pass through the porous, semipermeable membrand 14m of oxygenator unit 14. This safetymeans-66 comprises a liquid-filled tube having a rigid, tubular extension 68 of line 64, which safetymeans functions as a pressure limiting device in the manner described in U.S. Pat. application Ser. No."390,567, filed Aug..22, 1973 by Ronald J. Leonard." I I I Oxygenator unit holder 12 also comprises, top and bottom plates 12p, 12q, and sidewalls ,-l2s,'which are secured together in .the manner previouslydescribed for plate 42, by means of nuts 12n which fit on:bolts 12b, and detent means 12d. Plate 12p is attached.by glueing or welding to bracket 35. Oxygenator unit 14 is optionally not enclosed along its rear, blood flow side.

In the specific embodiment shown therein, inlet manifold port 44 does not pass straight through plate 42,

but makes two right angle turns as shown in FIG. 4 so as to pass through a U-shaped heater block 69 which is mounted within cover 70 which, in turn, is carried by plate 42. Heater block 69, through which inlet manifold port 44 passes as an elongated channel, provides means to warm the oxygen gas entering into the oxygenator unit to a predetermined temperature. A typical heater block 69 usable herein can be a typical 45 watt, 120 volt, 3-ohm electric cartridge heater. Conduit 65 also passes through heater block 69 to communicate with manifold port 44 therein.

Heater block 69 is controlled by two thermostats 72, electrically connected together so that the disconnection of either thermostat deactivates heater block 69. The purpose of this is to provide a high degree of assurance that the oxygen gas is not overheated, since oxygen gas temperatures in excess of 42 C. could cause serious damage to blood in the oxygenator. Fuse 73 is also provided for added safety.

Insulating wall 74 prevents undue heat loss from heater block 69. If desired, an alarm means can be provided to activate alarm buzzer 78 when a pressure switch 79 mounted in fluid communication with the inlet manifold port 44 is not sensing a gas pressure in excess of a standard pressure of at least 6 inches of water, which is equivalent to approximately 5 liters per minute of oxygen flow through port 44 when the port diameter is about V4 inch. This arrangement may comprise a conventional relay 80 activating buzzer 78 when the predetermined gas overpressureis not sensed.

Port 82 is defined completely through plate 42 and cover 70 to permit the passage of inflation line 84 of oxygenator unit 14 therethrough. Inflation line 84 communicates with an inflatable shim inside of oxygenator 14 which can be used to pressurize the screening lavers 14s and membrane layers 14m together to counter-balance the tendency of the oxygenator unit to expand due to the blood pressure pushing the screening and membranes apart.

The inflatable shim may be placed at the midpoint of the stack of screening and membrane layers, or it can be of U-shaped cross-sectional construction to provide a pair of expansion members on each side of the stack for the same purpose. Other designs of inflatable shim can also be used.

Typically, unit holder 12 is positioned at an angular relationship to the vertical by bracket 35, to elevate the blood outlet as shown in FIG. 4, to facilitate the priming of the oxygenator unit with blood or saline solution. The angular relationship facilitates the removal of all air bubbles from the oxygenator unit into outlet line 18 during priming. Bottom plate l2q has a beveled lower edge 86 so that unit holder 12 assumes the same angu- 6 larrelationship to theverticalxwhen resting on a horizontal surface, before being hung by bracket 35 on arm 43. Thus, unit holder 12 can be conveniently loaded withan oxygenator unit, and the unit primed with saline solution, prior to hanging on arm 43.

The above has been offered for illustrative purposes only, and is not intended to limit the invention of this application which is as described in the claims below.

What is claimed is:

l.In 'a blood oxygenator unit which defines a first plurality of blood flow channels and a second plurality of oxygen flow channelsin interleaving relation to said first flow channels, said first and second flow channels beingseparated by a semipermeable membrane, and an outer casing enclosing said membrane and said flow channels, said outer casing having separate blood and oxygen inlets and outlets, the improvement wherein said oxygen inlet comprises a transversely elongated port defined in said casing, positioned to directly expose one end of all of said plurality of said second flow channels to the exterior of said casing, whereby simple connection of said second flow channels to an oxygen line is prevented.

2. The blood oxygenator unit of claim 1 in which said semipermeable membrane is a porous, hydrophobic material capable of preventing the passage of blood while permitting the passage of oxygen and carbon dioxide therethrough.

3. In an oxygenator for blood which comprises: bracket means removably holding membrane means for the oxygenation of blood, means for conveying blood from a patient through said membrane means mounted in said bracket means in a first flow path and back to said patient, means for supplying oxygen gas through said membrane means mounted in said bracket means in a second flow path separate from said first flow path and separated therefrom in said membrane means by a semi-permeable membrane, said second flow path comprising in said membrane means a plurality of parallel flow channels, the improvement comprising, in combination: said bracket means carrying plate means selectively removably engaging said membrane means for oxygenation of blood, said plate means including means defining an oxygen inlet manifold port positioned to directly communicate, in engaging position, with said parallel flow channels of the second flow path in said membrane means, to provide a sealed oxygen flow path through said plate into said oxygenator unit.

4. The oxygenator of claim 3 which carries means for heat exchanging in flow communication with blood passing through said oxygenator.

5. The oxygenator of claim 3, the improvement further comprising said parallel flow channels of the second flow path being directly exposed to the exterior of said membrane means for the oxygenation of blood, and said second flow path of the membrane means having an inlet which is transversely elongated to facilitate said exposure, said oxygen inlet manifold port means being proportioned to surround and seal said inlet to provide said sealed, oxygen flow path.

6. The oxygenator of claim 5 which includes safety means carried by said oxygenator for preventing the pressure of said oxygen gas from reaching a level sufficient to cause gas bubbles to pass through said membrane and to enter said first flow path, and in which said oxygen inlet manifold port means is in fluid communication with a conduit for providing gas pressure 7 communication between said oxygen flow saidsafety means.

7. The oxygenator of claim 5, the improvement further comprising said plate means, in its position of engagement with the membrane means for oxygenation of blood, being positioned to be spaced from and to define an unbroken wall over the outlet of said second flow path of the membrane means, whereby exhaust gas from said second flow path has unrestricted exit in a plurality of directions between said plate means and membrane means, to prevent accidental obstruction said outlet of the second flow path.

8. The oxygenator of claim 7 in which an O-ring seal path and is positioned between said oxygen inlet manifold port means and the inlet of the second flow path of the membrane means.

- 9. The oxygenator of claim 8 in which said semipermeable membrane is a porous, hydrophobic material capable of preventing the passage of blood while permitting the passage of oxygen and carbon dioxide therethrough.

10. The oxygenator of claim 9, the improvement further comprising said membrane means for the oxygenation of blood being disposed in angular relationship to the vertical, to elevate the first flow path outlet from said membrane means above all other flow portions in said membrane means, to facilitate gas bubble removal from the first flow path. 

1. IN A BLOOD OXYGENATOR UNIT WHICH DEFINES A FIRST PLURALITY OF BLOOD FLOW CHANNELS AND A SECOND PLURALITY OF OXYGEN FLOW CHANNELS IN INTERLEAVING RELATION TO SAID FIRST FLOW CHANNELS, SAID FIRST AND SECOND FLOW CHANNELS BEING SEPARATED BY A SEMIPERMEABLE MEMBRANE, AND AN OUTER CASING ENCLOSING SAID MEMBRANE AND SAID FLOW CHANNELS, SAID OUTER CASING HAVING SEPARATE BLOOD AND OXYGEN INLETS AND OUTLETS, THE IMPROVEMENT WHEREIN SAID OXYGEN INLET COMPRISES A TRANSVERSELY ELONGATED PORT DEFINED IN SAID CASING, POSITIONED TO DIRECTLY ESPOSE ONE END OF ALL OF SAID PLURALITY OF SAID SECOND FLOW CHANNELS TO THE EXTERIOR OF SAID CASING, WHEREBY SIMPLE CONNECTION OF SAID SECOND FLOW CHANNELS TO AN OXYGEN LINE IS PREVENTED.
 2. THE BLOOD OXYGENATOR UNIT OF CALIM 1 IN WHICH SAID SEMIPERMEABLE MEMBRANE IS A POROUS, HYDROPHOBIC MATERIAL CAPABLE OF PREVENTING THE PASSAGE OF BLOOD WHILE PERMITTING THE PASSAGE OF OXYGEN AND CARBON DIOXIDE THERETHROUGH.
 3. In an oxygenator for blood which comprises: bracket means removably holding membrane means for the oxygenation of blood, means for conveying blood from a patient through said membrane means mounted in said bracket means in a first flow path and back to said patient, means for supplying oxygen gas through said membrane means mounted in said bracket means in a second flow path separate from said first flow path and separated therefrom in said membrane means by a semi-permeable membrane, said second flow path comprising in said membrane means a plurality of parallel flow channels, the improvement comprising, in combination: said bracket means carrying plate means selectively removably engaging said membrane means for oxygenation of blood, said plate means including means defining an oxygen inlet manifold port positioned to directly communicate, in engaging position, with said parallel flow channels of the second flow path in said membrane means, to provide a sealed oxygen flow path through said plate into said oxygenator unit.
 4. The oxygenator of claim 3 which carries means for heat exchanging in flow communication with blood passing through said oxygenator.
 5. The oxygenator of claim 3, the improvement further comprising said parallel flow channels of the second flow path being directly exposed to the exterior of said membrane means for the oxygenation of blood, and said second flow path of the membrane means having an inlet which is transversely elongated to facilitate said exposure, said oxygen inlet manifold port means being proportioned to surround and seal said inlet to provide said sealed, oxygen flow path.
 6. The oxygenator of claim 5 which includes safety means carried by said oxygenator for preventing the pressure of said oxygen gas from reaching a level sufficient to cause gas bubbles to pass through said membrane and to enter said first flow path, and in which said oxygen inlet manifold port means is in fluid communication with a conduit for providing gas pressure communication between said oxygen flow path and said safety means.
 7. The oxygenator of claim 5, the improvement further comprising said plate means, in its position of engagement with the membrane means for oxygenation of blood, being positioned to be spaced from and to define an unbroken wall over the outlet of said second flow path of the membrane means, whereby exhaust gas from said second flow path has unrestricted exit in a plurality of directions between said plate means and membrane means, to prevent accidental obstruction of said outlet of the second flow path.
 8. The oxygenator of claim 7 in which an O-ring seal is positioned between said oxygen inlet manifold port means and the inlet of the second flow path of the membrane means.
 9. The oxygenator of claim 8 in which said semi-permeable membrane is a porous, hydrophobic material capable of preventing the passage of blood while permitting the passage of oxygen and carbon dioxide therethrough.
 10. The oxygenator of claim 9, the improvement further comprising said membrane means for the oxygenation of blood being disposed in angular relationship to the vertical, to elevate the first flow path outlet from said membrane means above all other flow portions in said membrane means, to facilitate gas bubble removal from the first flow path. 